U.S. patent number 6,813,402 [Application Number 10/076,302] was granted by the patent office on 2004-11-02 for fiber, probe and optical head of multiple optical path array type and methods for manufacturing the same.
This patent grant is currently assigned to Jasco Corporation. Invention is credited to Tsutomu Inoue, Yoshihito Narita.
United States Patent |
6,813,402 |
Narita , et al. |
November 2, 2004 |
Fiber, probe and optical head of multiple optical path array type
and methods for manufacturing the same
Abstract
It is an object of the present invention to provide a probe that
may correspond to various styles of measurement when used in
microscopes and that is also applicable to recording devices and an
optical head using the same, as well as to provide a method for
manufacturing such a probe in a simple and costless manner; for
achieving such objects, the method for manufacturing a multiple
optical path array type probe according to the present invention is
arranged in that in a light guiding material including a substrate
that functions as a clad and a light guiding path formed of a
component that functions as a core for guiding light or as a
waveguide, the light guiding material includes a plurality of light
guiding paths aligned to be parallel to each other within the
substrate that functions as a clad, and tip end portions of the
light guiding paths are sharpened through chemical etching of an
end surface that is orthogonal to the plurality of light guiding
paths.
Inventors: |
Narita; Yoshihito (Hachioji,
JP), Inoue; Tsutomu (Hachioji, JP) |
Assignee: |
Jasco Corporation (Tokyo,
JP)
|
Family
ID: |
18924274 |
Appl.
No.: |
10/076,302 |
Filed: |
February 19, 2002 |
Foreign Application Priority Data
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Mar 8, 2001 [JP] |
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2001-65665 |
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Current U.S.
Class: |
385/12;
977/862 |
Current CPC
Class: |
G02B
6/241 (20130101); G01Q 60/22 (20130101); G02B
6/245 (20130101); Y10S 977/862 (20130101) |
Current International
Class: |
G02B
6/245 (20060101); G02B 6/24 (20060101); G12B
21/06 (20060101); G12B 21/00 (20060101); G02B
006/12 () |
Field of
Search: |
;385/8-12,15,31,39,120,88,90,123,136,137,115 ;313/524
;29/850,837,852,830,843,863 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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|
A 2000-132856 |
|
May 2000 |
|
JP |
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A 2000-215499 |
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Aug 2000 |
|
JP |
|
A 2000-223767 |
|
Aug 2000 |
|
JP |
|
Other References
Yatsui et al., "Subwavelength-sized phase-change recording with a
silicon planar apertured probe", SPIE, vol. 3791, pp. 76-84, Jul.
1999. .
Lee et al., "Nanometric aperture arrays fabricated by wet and dry
etching of silicon for near-field optical storage application", J.
Vac. Sci. Technol. B, vol. 17, No. 6, pp. 2462-2466, Nov./Dec.
1999. .
Yatsui et al., "High-density-speed optical near-field
recording-reading with a pyramidal silicon probe on a contact
slider", Optics Letters, vol. 25, No. 17, pp. 1279-1281, Sep.
2000..
|
Primary Examiner: Ullah; Akm Enayet
Attorney, Agent or Firm: Oliff & Berridge, PLC
Claims
We claim:
1. A method for manufacturing a multiple optical path array type
probe in which in a light guiding material including a substrate
that functions as a clad and a light guiding path formed of a
component that functions as a core for guiding light or as a
waveguide, wherein the light guiding material includes a plurality
of light guiding paths aligned to be parallel to each other within
the single substrate that functions as a clad, and wherein the
light guiding material is arranged so that a light transmittance
preventing means is provided between the respective optical paths
so that light is prevented from being transmitted between the
respective optical paths, wherein tip end portions of the light
guiding paths are sharpened through chemical etching of an end
surface that is orthogonal to the plurality of light guiding paths,
and wherein mask of a light blocking material and apertures are
formed at tip end portion of the sharpened light guiding paths.
2. The method for manufacturing a multiple optical path array type
probe as claimed in claim 1, wherein the substrate that functions
as the clad of the light guiding material includes pure SiO.sub.2
and the light guiding paths of the light guiding material of a
material in which SiO.sub.2 includes components such as metal or
metal oxides, and wherein chemical etching is performed by
impregnating an end surface of the light guiding material into a
HF-NH.sub.4 type buffer solution for a specified period of
time.
3. A multiple optical path array type probe manufactured by using
the method for manufacturing a multiple optical path array type
probe as claimed in claim 1.
4. A multiple optical path array type probe in which in a light
guiding material including a substrate that functions as a clad and
a light guiding path formed of a component that functions as a core
for guiding light or as a waveguide, wherein the light guiding
material includes a plurality of light guiding paths aligned to be
parallel to each other within the single substrate that functions
as a clad, and wherein the light guiding material is arranged so
that a light transmittance preventing means is provided between the
respective optical paths so that light is prevented from being
transmitted between the respective optical paths, wherein tip end
portions of the light guiding paths are sharpened, and wherein mask
of a light blocking material and apertures are formed at tip end
portion of the sharpened light guiding paths.
5. A multiple optical path array type probe as claimed in claim 4,
wherein the substrate that functions as the clad of the light
guiding material includes pure SiO.sub.2 and the light guiding
paths of the light guiding material includes a material in which
SiO.sub.2 includes components such as metal or metal oxides.
6. A multiple optical path array type probe as claimed in claim 4,
wherein the respective light guiding paths are arranged in that an
interval between mutually adjoining light guiding paths is not more
than 20 .mu.m.
7. A multiple optical path array type probe as claimed in claim 4,
wherein the light transmittance preventing means is a thin film
layer made of gold.
8. A multiple optical path array type probe as claimed in claim 4,
wherein a plurality of light guiding paths are arranged in a linear
form on an end surface that is orthogonal to the plurality of light
guiding paths of the light guiding material.
9. A multiple optical path array type probe as claimed in claim 4,
wherein a plurality of light guiding paths are arranged in a
latticed form on an end surface that is orthogonal to the plurality
of light guiding paths of the light guiding material.
10. A multiple optical path array type probe as claimed in claim 4,
wherein a plurality of light guiding paths are arranged in a spiral
form on an end surface that is orthogonal to the plurality of light
guiding paths of the light guiding material.
11. A multiple optical path array type probe as claimed in claim 4,
wherein the probe of multiple optical path is any one of a AFM
probe, STM probe or a near-field probe.
12. A multiple optical path array type probe as claimed in claim 4,
wherein a mask of a light blocking material exhibiting ductility is
formed at tip end portion of the sharpened light guiding paths, and
wherein the probe further comprises holding materials for adjusting
an amount of pressing, when forming an aperture of a specified size
on all of the plurality of light guiding paths upon pressing the
mask against a planar surface, to be of an aperture diameter that
is formed upon pressing the same against the planar surface.
13. An multiple optical path array type optical head arranged to be
an optical head for recording/reading information for a near-field
optical memory by using the multiple optical path array type probe
as claimed in claim 4.
14. The multiple optical path array type optical head as claimed in
claim 13, wherein the probe comprises distance holding materials
for securing a distance between a tip end of the probe and a
surface of a recording material for recording/reading
information.
15. A multiple optical path array type fiber in which in a light
guiding material including a substrate that functions as a clad
elongated in a linear manner and a light guiding path formed of a
component that functions as a core for guiding light into the
linear substrate or as a waveguide and extending in an extending
direction of the substrate, wherein the light guiding material
includes a plurality of light guiding paths aligned to be parallel
to each other within the single substrate that functions as a clad,
wherein the light guiding material is arranged so that a light
transmittance preventing means is provided between the respective
optical paths so that light is prevented from being transmitted
between the respective optical paths, and wherein mask of a light
blocking material and apertures are formed at tip end portion of
the sharpened light guiding paths.
16. A multiple optical path array type probe manufactured by using
the method for manufacturing a multiple optical path array type
probe as claimed in claim 2.
17. A multiple optical path array type probe as claimed in claim
15, wherein the light transmittance preventing means is a thin film
layer made of gold.
18. The method for manufacturing a multiple optical path array type
probe as claimed in claim 1, wherein the light transmittance
preventing means is a thin film layer made of gold.
Description
RELATED APPLICATIONS
The present application claims the priority of Japanese Patent
Application No.2001-65665 filed on Mar. 8, 2001, which is
incorporated herein.
FIELD OF THE INVENTION
The present invention relates to improvements in multiple optical
path array type probes including a plurality of light guiding
paths, multiple optical path array type optical heads employing the
same, and particularly in refinements of distances between optical
paths included in probes, and in methods for manufacturing the
same.
BACKGOUND OF THE INVENTION
It was generally the case with devices or equipments in which
optical techniques are applied that limits in their performances
were determined by wavelengths of light. For instance, it is
impossible to observe any objects that are smaller than wavelengths
of light by using a general optical microscope, and its resolution
is limited.
Optical memories and similar were also known as recording materials
for recording information applicable to computers or the like by
using light. It was the case with such optical memories that upper
limits of information recording densities were determined by
diffraction limits of light and only marks of several hundreds of
nm and thus approximating wavelengths of light could be
recorded/read.
Novel techniques are being developed for such devices and
equipments employing light in these years with which it is possible
to get rid of restraints of wavelengths of light. There are
techniques employing evanescent light or near-field light and are
being paid attention to in view of their applicability to objects
and regions that are smaller than wavelengths of light.
The following explanations will be made on the basis of an example
of a microscope in which evanescent light or near-field light is
applied. Known measuring theories are such in which a field of
evanescent light or near-field light is generated on a sample
surface into which a tip end portion of a probe is inserted for
accordingly scattering the evanescent light or near-field light and
thus measuring the scattered light, or such in which a field of
evanescent light or near-field light is generated at the tip end
portion of the probe whereupon the evanescent light or near-field
light of the tip end portion of the probe is hit against the sample
surface for scattering the evanescent light or near-field light and
accordingly measuring the scattered light.
However, conventionally used probes were arranged in that a single
light guiding path was formed in a single probe so that only one
tip end portion to be inserted into a field of evanescent light or
near-field light or only one tip end portion for generating such
evanescent light or near-field light was present as well. Thus, it
was time-consuming and energy-taking for observing surface
information within a specified range of an object to be measured or
an image on its a surface by using such a microscope with which
such a region smaller than wavelengths of light could be
observed.
While it is possible to perform optical analysis at high space
resolution when using evanescent light or near-field light,
excitation regions and measuring regions were partly overlapping in
conventional probes so that it was required in evaluation of
semiconductors to selectively measure emission of light right next
to the excitation region which, however, could not be realized.
In the field of optical memories, near-field optical recording
techniques are being paid attention to as compact recording devices
capable of recording a large volume of information without being
restrained by wavelengths of light for further improving recording
densities. According to the near-field optical recording
techniques, it is possible to perform recording/reading of an even
larger volume of information by using media of identical size as
those of conventional optical memories which is affected by
improvements in recording densities.
An arrangement of an optical head used in such optical memories in
which a plurality of near-field probes is aligned in a planar
manner is being actively studied. Manufacturing costs caused a
burden since a method was employed in which multi-staged
film-forming/etching processes were performed with respect to Si
wafers for manufacturing such probes.
Also, the accuracy of processing directly determined intervals
between members corresponding to tip end portions of the probes.
Thus, limits in correctness of shapes or intervals between tip end
portions were determined through accuracy of processing so that
intervals between tip end portions of probes of conventional
optical heads fell in the range of approximately 30 .mu.m and the
intervals were thus too large in view of recording densities.
However, it is extremely difficult to manufacture the intervals
between members corresponding to tip end portions of probes by
orders of several .mu.m, and developments in novel manufacturing
techniques were being desired. It was further impossible to apply
improved techniques related to throughputs as cultivated in
conventional techniques in the field of optical fibers when
employing techniques for performing such processing.
Shapes of tip end portions of probes that could be manufactured
were also limited.
The present invention has been made in view of the above subjects,
and it is an object thereof to provide a probe that may correspond
to various styles of measurement when used in microscopes and that
is also applicable to recording devices, an optical head using the
same, and a method for manufacturing such a probe in a simple and
costless manner.
SUMMARY OF THE INVENTION
For achieving such objects, the method for manufacturing a multiple
optical path array type probe according to the present invention is
arranged in that in a light guiding material including a substrate
that functions as a clad and a light guiding path formed of a
component that functions as a core for guiding light or as a
waveguide, the light guiding material includes a plurality of light
guiding paths aligned to be parallel to each other within the
substrate that functions as a clad, and tip end portions of the
light guiding paths are sharpened through chemical etching of an
end surface that is orthogonal to the plurality of light guiding
paths.
In the method for manufacturing a multiple optical path array type
probe of the present invention, the substrate that functions as the
clad of the light guiding material consists of pure SiO.sub.2 and
the light guiding paths of the light guiding material of a material
in which SiO.sub.2 includes components such as metal or metal
oxides, and chemical etching is performed by impregnating an end
surface of the light guiding material into a HF--NH.sub.4 type
buffer solution for a specified period of time.
It is preferable to manufacture the multiple optical path array
type probe according to the present invention by using the above
method for manufacturing a multiple optical path array type
probe.
The multiple optical path array type probe according to the present
invention is arranged in that in a light guiding material including
a substrate of pure SiO.sub.2 that functions as a clad and a light
guiding path of SiO.sub.2 including components such as metal or
metal oxides formed of a component that functions as a core of a
material for guiding light or as a waveguide, the light guiding
material includes a plurality of light guiding paths aligned to be
parallel to each other within the substrate that functions as a
clad, and tip end portions of the light guiding paths are
sharpened.
The multiple optical path array type probe according to the present
invention is arranged in that in a light guiding material including
a substrate that functions as a clad and a light guiding path
formed of a component that functions as a core for guiding light or
as a waveguide, the light guiding material includes a plurality of
light guiding paths aligned to be parallel to each other within the
substrate that functions as a clad, tip end portions of the light
guiding paths are sharpened, and the respective light guiding paths
are arranged in that an interval between mutually adjoining light
guiding paths is not more than 20 .mu.m.
In the multiple optical path array type probe according to the
present invention, it is preferable that the light guiding material
is arranged in that a light transmittance preventing means is
provided between the respective optical paths so that light is
prevented from being transmitted between the respective optical
paths.
In the multiple optical path array type probe according to the
present invention, it is preferable that the light transmittance
preventing means is a thin film layer made of gold.
In the multiple optical path array type probe according to the
present invention, it is preferable that a plurality of light
guiding paths are arranged in a linear form on an end surface that
is orthogonal to the plurality of light guiding paths of the light
guiding material.
In the multiple optical path array type probe according to the
present invention, it is preferable that a plurality of light
guiding paths are arranged in a latticed form on an end surface
that is orthogonal to the plurality of light guiding paths of the
light guiding material.
In the multiple optical path array type probe according to the
present invention, it is preferable that the probe of multiple
optical path is any one of a AFM probe, STM probe or a near-field
probe.
In the multiple optical path array type probe according to the
present invention, it is preferable that a mask of a light blocking
material exhibiting ductility is formed at tip end portion of the
sharpened light guiding paths, and wherein the probe further
comprises holding materials for adjusting an amount of pressing,
when forming an aperture of a specified size on all of the
plurality of light guiding paths upon pressing the mask against a
planar surface, to be of an aperture diameter that is formed upon
pressing the same against the planar surface.
The multiple optical path array type optical head according to the
present invention is arranged to be an optical head for
recording/reading information for a near-filed optical memory by
using the above multiple optical path array type probe.
In the multiple optical path array type optical head according to
the present invention, it is preferable that the probe preferably
comprises distance holding materials for securing a distance
between a tip end of the probe and a surface of a recording
material for recording/reading information.
The multiple optical path array type fiber according to the present
invention is arranged in that in a light guiding material including
a substrate that functions as a clad elongated in a linear manner
and a light guiding path formed of a component that functions as a
core for guiding light into the linear substrate or as a waveguide
and extending in an extending direction of the substrate, the light
guiding material includes a plurality of light guiding paths
aligned to be parallel to each other within the substrate that
functions as a clad.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal sectional view of a multiple optical path
array type probe representing one embodiment of the present
invention.
FIGS. 2(a)-2(c) are vertical sectional views of embodiments of the
multiple optical path array type probe according to the present
invention.
FIGS. 3(a)-3(b) are enlarged photographs of the multiple optical
path array type probe manufactured in accordance with the
manufacturing method of the present invention.
FIGS. 4(a)-4(c) are explanatory views or explaining an aperture of
a mask provided at the probe.
FIGS. 5(a)-5(d) are explanatory views for forming a holding
material at the multiple optical path array type probe of the
present invention.
FIGS. 6(a)-6(c) are schematic views of embodiments of the multiple
optical path array type optical head.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The multiple optical path array type probe of the present invention
will now be explained on the basis of one embodiment of the present
invention.
FIG. 1 illustrates a longitudinal sectional view of a multiple
optical path array type probe representing one embodiment of the
present invention.
The multiple optical path array type probe 2 illustrated in the
drawing is arranged in that in a light guiding material including a
substrate 4 that functions as a clad and a light guiding path 6
formed of a component that functions as a core for guiding light or
as a waveguide, wherein the light guiding material includes a
plurality of light guiding paths 6 aligned to be parallel to each
other within the substrate 4 that functions as a clad, with tip end
portions of the light guiding paths being sharpened.
An outer periphery of the clad may be, if necessary, covered by a
protection layer 8 made of resin or similar.
It should be noted that it is preferable that the intervals between
mutually adjoining light guiding paths 6 of the multiple optical
path array type probe 2 of the present invention are not more than
20 .mu.m, and more preferably not more than 10 .mu.m.
In this manner, the smaller the intervals between light guiding
paths 6 are, the higher the density of the light guiding paths will
become so that it is possible to increase a measuring range that
may be measured within an unit time and to perform more detailed
measurement of an object to be measured when used in a measuring
device such as a microscope. When used in an optical head as will
be described later in details, it will be possible to improve the
recording density.
It is preferable that the multiple optical path array type probe 2
of the present invention is arranged in that its substrate that
functions as a clad is made of pure SiO.sub.2 and in that the light
guiding paths formed of a component that functions as a core for
guiding light or a waveguide is made of a material in which
SiO.sub.2 includes components such as metal or metal oxides.
By forming the light guiding paths of such a material in which
quartz is included as a main component, sharpening of the light
guiding paths 6 may be performed upon chemical etching in the
manufacturing method as will be described later in details so that
it is possible to adjust the shape of all tip end portions of the
light guiding paths to be substantially uniform while it is further
possible to arbitrarily determine the shape of the tip end portions
of the light guiding paths. As for the intervals between light
guiding paths, intervals between light guiding paths may be
directly defined by intervals that are preliminarily adjusted and
manufactured when manufacturing light guiding materials that
undergo chemical etching, and it is accordingly possible to easily
adjust the intervals between light guiding paths to be of fine
intervals.
Since a probe that is manufactured by using such a material is
applicable to conventional techniques related to optical fibers or
the like as it is, it is also of advantage that it enables
application to polarization or broad wavelength bands.
It should be noted that a material of the fiber might be one of
quartz glass, chalcogenide glass (for infrared), fluoride glass,
silicon or plastic. When using, for instance, quartz glass, a core
portion is formed of SiO.sub.2 doped with Ge while a clad portion
is formed of SiO.sub.2 doped with F.
Since such multiple optical path array type probes were
conventionally manufactured by using Si probes, once a shape of the
tip end of the light guiding paths was preliminarily determined by
processing Si, the manufacture was limited to that very shape
whereas the present invention enables it to freely select the shape
from product to product. Moreover, since the intervals between
respective tip end portions of the light guiding paths are not
restrained by the accuracy of processing Si, it is possible to set
minute intervals by orders of several .mu.m.
It should be noted that it is necessary to consider the problem of
transmittance of light occurring between light guiding paths.
Conventionally, intervals between light guiding paths were
approximately 30 .mu.m and thus remarkably larger than wavelengths
of light, and it was not necessary to consider the order of photons
transmitting through a single light guiding path jumping over to
adjoining light guiding paths; however, with the intervals between
light guiding paths becoming several .mu.m, which could be realized
by the present invention, and only several times larger than
wavelengths of light and thus close to wavelengths of light, a
phenomenon in which photons jump over to adjoining light guiding
paths are well possible.
Thus, the present invention has provided light transmittance
preventing means between respective light guiding paths of the
light guiding material to obtain an arrangement in which light does
not mutually transmit between the respective light guiding paths
(in which no photons jump over).
In FIG. 1, light transmittance preventing means 10 are provided
between respective light guiding paths 6. In one of the embodiments
as illustrated in FIG. 1, light transmittance preventing means 10
are also provided between the protection layer 8 and the light
guiding paths 6.
Since a 1:1 relationship may be achieved of an entrance and an exit
of photons in the light guiding paths 6, high accuracy may also be
maintained even in techniques for measuring or recording.
It should be noted that the light transmittance preventing means 10
are arranged of thin film layers of gold in the multiple optical
path array type probe of the present embodiment. In this manner, it
is possible to provide light transmittance preventing means through
relatively simple methods such as preliminarily evaporating gold on
a surface of the light guiding paths.
FIG. 2 illustrates a vertical sectional view of one embodiment of
the multiple optical path array type probe of the present
invention. It should be noted that components corresponding to
components identical to those of FIG. 1 are marked with the same
reference numerals and explanations thereof will be omitted.
As illustrated in (a) of the same drawing, it is preferable that a
plurality of light guiding paths 6 are disposed in a linear manner
on an end surface that is orthogonal to the plurality of light
guiding paths 6 of the light guiding material in the multiple
optical path array type probe of the present invention.
If the light guiding paths 6 are disposed in a linear manner like
this case, it is possible to achieve an advantage in that
positional alignment of the respective light guiding paths 6 may be
easily performed, and if such a probe is used, for instance, as an
optical head, one light guiding path may be used for reading track
information while the remaining light guiding paths may be used for
recording/reading of information.
As illustrated in FIG. 2(b), it is also preferable that a plurality
of light guiding paths are disposed in a latticed manner on an end
surface that is orthogonal to the plurality of light guiding paths
of the light guiding material in the multiple optical path array
type probe of the present invention.
Similar to the linear arrangement, such a multiple optical path
array type probe is also advantaged in that positional alignment of
the respective light guiding paths 6 may be easily performed when
used in equipments, and moreover, simultaneous measurement may be
performed by the plurality of light guiding paths when using the
same for measuring in, for instance, a microscope so as to
remarkably increase the measuring range of which measurement may be
performed per unit time. When using such a probe as an optical
head, not only can one light guiding path be used for reading track
information while the remaining light guiding paths are used for
recording/reading of information, but also is it possible to
achieve more refined recording densities upon adjusting angles of
use when compared to those of linear arrangement as well as
increase the amount of recording/reading information of a single
action.
Further, as illustrated in FIG. 2(c), it is also preferable that a
plurality of light guiding paths are disposed in a spiral manner on
an end surface that is orthogonal to the plurality of light guiding
paths of the light guiding material in the multiple optical path
array type probe of the present invention.
While positional alignment of the respective light guiding paths 6
may become somewhat difficult in such a multiple optical path array
type probe when used in equipments, when using the same for
measurement by using, for instance, a microscope, the probe may be
rotated with a central axis of the probe being the center so that
measurement of a range corresponding to substantially all of a
sectional portion of the probe may be performed at substantially
all points.
While such a multiple optical path array type probe of the present
invention is applicable to a variety of purposes, it is preferable
that this be an AFM probe, STM probe or a near-field probe.
When applying the multiple optical path array type probe of the
present invention of the above-described shape to an optical
measuring device such as a microscope, one light guiding path may
be used for exciting an object to be measured for observing a
condition in which an excited region such as a near-field gradually
expands. It will also be possible to observe, for instance, how a
carrier for exciting an object to be measured moves. Since planar
information related to objects to be measured may be observed which
had so far been impossible, various applications thereof are
possible.
A method for manufacturing the above explained multiple optical
path array type probe of the present invention will now be
explained.
Manufacturing Method
The multiple optical path array type probe of the present invention
is arranged in that in a light guiding material including a
substrate that functions as a clad and a light guiding path formed
of a component that functions as a core for guiding light or as a
waveguide, the light guiding material includes a plurality of light
guiding paths aligned to be parallel to each other within the
substrate that functions as a clad, and tip end portions of the
light guiding paths are sharpened through chemical etching of an
end surface that is orthogonal to the plurality of light guiding
paths.
Explanations will follow based on a concrete example of
manufacturing.
As for the light guiding material, a SiO.sub.2 glass fiber with a
clad made of pure SiO.sub.2 glass and a core of SiO.sub.2 glass
including GeO.sub.2 is used. In the clad of the fiber, a plurality
of light guiding paths comprised of a core is aligned in parallel
with each other.
An etching process for reducing a clad diameter is performed as a
preliminary stage of etching for sharpening. More particularly,
upon cutting one end of the fiber and impregnating the same into a
buffer solution, an etching speed may vary depending on an amount
of doping from a peripheral portion to a central portion of the
core. For instance, in case an end surface of a high density doped
fiber with an amount of addition of GeO.sub.2 being 25 mol % is
etched by using a buffer solution mixed at a volumetric ratio of HF
(50%):NH.sub.4 F (40%):H.sub.2 O=X:1:1, the core will be concaved
when X<1.7 is satisfied at room temperature (approximately
23.degree. C.) while it may be sharpened when X>1.7 is
satisfied.
Thus, the clad diameter is reduced in a first stage by using a
buffer solution of X=1.7 (in which the etching speeds of the clad
and the core are identical). The clad diameter may be controlled
upon controlling conditions such as etching time.
Next, sharpening is performed in a second stage by using a buffer
solution of X>1.7. In case, for instance, X=5 is satisfied, an
angle of sharpening will be 25.degree. and the radius of curvature
of the tip end will become minimum which is not more than 5 nm
after elapse of 1 hour. It should be noted that while the radius of
curvature of the tip end increases to approximately 10 nm when the
optimal time is exceeded, the radius would not increase any
further. In case of X=10, the angle of sharpening will be minimum
which is 20.degree..
The tip end of the light guiding material thus formed includes a
flat head light guiding material as illustrated in FIG. 1 and a
plurality of sharp head light guiding paths provided on an end
surface portion of the flat head surface.
An enlarged photograph of a multiple optical path array type probe
that has been actually manufactured in accordance with the method
for manufacturing the multiple optical path array type probe of the
present invention is shown in FIG. 3. FIG. 3(a) is an enlarged view
of an overall end surface of the probe while FIG. 3(b) is an
enlarged view in which the light guiding path portion has been
further enlarged.
In this manner, since sharpening of light guiding paths is
performed through chemical etching in the method for manufacturing
a multiple optical path array type probe of the present invention,
all of the plurality of light guiding paths can be formed to be of
substantially arbitrary shape (angle of sharpening).
Since the light guiding material needs to be simply impregnated in
a buffer solution for a specified time in the present method for
manufacturing, easy manufacture is enabled, and it is possible to
remarkably reduce costs when compared to conventional methods for
manufacturing a multiple optical path array type probe.
It should be noted that the present invention is not limited to the
above-disclosed chemical etching only.
When treating evanescent light or near-field light by using such a
probe, masks were provided at tip end portions of the sharpened
light guiding paths of the probe wherein the masks were used upon
providing apertures that were smaller than wavelengths of
light.
FIG. 4 illustrates an explanatory view for explaining such
apertures of masks formed at the probe.
As illustrated in (a) of the same drawing, a mask 22 made of a
light blocking material is provided at the tip end portions 20 of
the light guiding paths, and an aperture 24, which is smaller than
wavelengths of light, is provided as well.
While various methods are known for forming such an aperture, one
method that could be simply performed was a method in which an
aperture was formed by pressing the mask against a planar
surface.
In this method, the mask 22 is formed on the tip end portion 20 of
the light guiding path by using a light blocking material
exhibiting ductility as illustrated in FIG. 4(b). As illustrated in
FIG. 4(c), the tip end portion is pressed against a planar surface
26 for obtaining an aperture of desired size.
While devices or jigs for performing pressing while measuring sizes
of apertures were conventionally known, such operations of forming
apertures required extreme preciseness and were thus quite
complicated.
In contrast thereto, the present invention has enabled an
arrangement in which a pressing method, which simplifies operations
for forming such apertures, can be employed.
In the multiple optical path array type probe of the present
invention, it is preferable that a mask is formed of a light
blocking material exhibiting ductility at tip end portion of the
sharpened light guiding paths, and that the probe further comprises
holding materials for adjusting an amount of pressing, when forming
an aperture of a specified size on all of the plurality of light
guiding paths upon pressing the mask against a planar surface, to
be of an aperture diameter that is formed upon pressing the same
against the planar surface.
Such a holding material may be formed by preliminarily arranging
the same to the light guiding material prior to chemical
etching.
First, it should preliminarily be determined to what extent the
light guiding path is to be projected from the end surface of the
probe, the degree of its sharpening angle and of its length. Upon
determining these points, the density of the buffer solution to be
used will be determined, and it is further determined what kind of
treatment shall be performed for what length of time for obtaining
such length and sharpening angle.
Since the size of the aperture diameter of the tip end portions of
the light guiding paths is determined by the degree of projection
of the holding material from the end surface of the probe, the
amount of projection of the holding material that is to be the
desired aperture diameter can inversely be calculated from the
determined length, and the holding material is formed of a material
that is not to be eroded through chemical etching to become the
inversely calculated amount of projection.
FIG. 5 illustrates an explanatory view when forming such a holding
material. It should be noted that portions corresponding to
components that are identical to those of FIG. 1 are marked with
identical reference numerals and explanations thereof are
omitted.
A schematic longitudinal sectional view of the multiple optical
path array type probe of the present invention is illustrated in
(a) of the same drawing. The light guiding material as illustrated
herein comprises holding materials 30 by an amount of projection as
inversely calculated from the sharpening angle and length of the
light guiding paths as preliminarily determined. The material that
is not eroded through chemical etching may be formed by using a
generally known material. In the present embodiment, the holding
materials are formed of boron. The holding materials may be formed
by making boron be contained in SiO.sub.2 that is to become the
clad material at high density, or boron may be alternatively used
singly.
When performing chemical etching of such a light guiding material,
the tip end portions of the light guiding paths are sharpened while
the holding materials remain as illustrated in FIG. 5(b). As
illustrated in FIG. 5(c), the mask 32 is then formed on the
sharpened light guiding paths of a light blocking material
exhibiting ductility upon performing treatments such as evaporating
gold.
When the tip end portions of the light guiding paths are then
pressed against the planar surface 34 as illustrated in FIG. 5(d),
the holding materials prevent the light guiding paths from being
excessively pressed against the planar surface 34 so that all tip
end portions of the light guiding paths may be formed with
apertures of substantially desired size.
It should be noted that the holding materials may be formed on the
entire outer periphery of the end surface portion of the light
guiding material that undergoes chemical etching or only on several
spots of the outer periphery, and there are not particular limits
as long as the arrangement is capable of preventing the tip end
portions of the light guiding paths from being excessively pressed
against the planar surface 34 for forming apertures of
substantially desired sizes on the tip end portions of the light
guiding paths.
The above-explained multiple optical path array type probe of the
present invention may be favorably used as an optical head for
recording/reading information on a near-field optical memory.
FIG. 6 illustrates a schematic view of one embodiment of a multiple
optical path array type optical head. It should be noted that
components corresponding to components identical to those of FIG. 1
are marked with the same reference numerals and explanations
thereof will be omitted.
As illustrated in the drawing, when arranging a multiple optical
path array type optical head by using the multiple optical path
array type probe of the present invention, it is preferable that
its outer shape is plate-like. In case its shape is plate-like, it
is possible to achieve downsizing of a recording device for
performing recording onto the recording material.
While various methods for manufacturing such a plate-like multiple
optical path array type probe may be employed, one example is a
method as illustrated in FIG. 6(b) in which an elongated light
guiding material is employed which one end surface undergoes
chemical etching for sharpening the light guiding paths 6 which are
then cut at a desired thickness, or it may alternatively be a
method in which a light guiding material that has preliminarily
been formed in a plate-like shape undergoes chemical etching.
It should be noted that in the method employing an elongated light
guiding material, a plurality of multiple optical path array type
optical heads might be manufactured by repeatedly performing
chemical etching of the end surface and cutting after cutting the
material once.
In the multiple optical path array type optical head of the present
invention, it is preferable that distance holding materials 36 for
securing a distance between tip ends of the probe and the recording
material surface for recording/reading information are provided as
illustrated in FIG. 6(c).
Such distance holding materials may be formed, similar to the
holding materials, by using a manufacturing method using a material
that is not eroded through chemical etching.
That is, it is possible to inversely calculate how to maintain the
distance with respect to the recording material on the basis of the
projection length of the light guiding paths so that the holding
materials may be formed of a material that is not eroded through
chemical etching to become the amount of projection obtained
through inversed calculation.
In the multiple optical path array type optical head of the present
invention, it is alternatively possible to provide holding
materials on the entire outer periphery of the light guiding
material or on several spots thereof whereupon an amount of erosion
of portions of the clad or the light guiding paths is adjusted
through chemical etching so as to use the remaining holding
materials as the distance holding materials as they are.
It should be noted that it is preferable to set the distance
between the tip end portions of the light guiding paths and the
recording surface of the recording material to be in the range of
10 to 30 nm in the thus provided distance holding materials. This
is because this range makes it possible to favorably use near-field
light.
As explained so far, according to the method for manufacturing a
multiple optical path array type probe of the present invention, it
is possible to manufacture probes with distances between light
guiding paths being extremely fine in an easy manner.
Moreover, according to the method for manufacturing a multiple
optical path array type probe, the multiple optical path array type
probe and the multiple optical path array type optical head of the
present invention, it is possible to provide an arbitrary number of
light guiding paths while it takes only as much trouble as
manufacturing a single probe.
Since the shape of the array type near-field probe can be freely
controlled when compared to a case in which they are formed of Si
base, the transmittance may be improved to an equivalent level as
those of conventional fiber type near-field probes and may
additionally be manufactured as low costs.
When applying the multiple optical path array type probe of the
present invention to optical measuring equipments, planar
distribution of emission, which is generated upon excitation of a
region that is not larger than a wavelength of light on a single
spot, can be simultaneously measured at a resolution that is not
more than the wavelength.
As explained so far, according to the method for manufacturing a
multiple optical path array type probe of the present invention, it
is possible to easily manufacture a multiple optical path array
type probe provided with an arbitrary number of light guiding
paths.
According to the multiple optical path array type probe and the
multiple optical path array type optical head of the present
invention, the transmittance may be improved to a level equivalent
to that of conventional fiber type near-field probes.
* * * * *